1. Field of the Invention
The present invention relates to an illumination optical system and an image projection device.
2. Description of the Related Art
Conventionally, there is known an image projection device that causes an image forming unit to generate an image to be projected by using a light emitted from a light source on the basis of image data received from a personal computer (PC) or a video camera, etc. and projects the generated image on a projection surface, such as a screen, to display the image on the projection surface. Such an image projection device is required to be capable of projecting an image on a large screen and reducing the distance between the image projection device and the projection surface as short as possible, and image projection devices enabling a short projection distance have been developed.
In an image projection device, a lens unit for expanding or compressing a light from a light source is arranged on a path of light from the light source to an image forming unit; therefore, the lens unit is required to be accurately fixed to an enclosure. For example, in an image projection device disclosed in Japanese Patent Application Laid-open No. 2005-266702, a lens unit is fixed in such a way that the lens unit is inserted into a holding unit formed on an enclosure, and is pushed against the holding unit by a leaf spring member. Furthermore, in an image projection device disclosed in Japanese Patent Application Laid-open No. 2004-117931, an elastic member for pushing a lens unit in a direction of the optical axis and another elastic member for pushing the lens unit in a vertical direction are disposed.
However, in the image projection devices enabling a short projection distance, a slight misalignment of the lens unit causes a large projection error; therefore, the fixation of the lens unit as described above is required to be performed with higher accuracy.
Therefore, there is a need for an illumination optical system and image projection device that are capable of fixing a lens unit located on a path of light from a light source to an image forming element with higher accuracy.